#include <bits/stdc++.h>
using namespace std;

int n;
vector<int> a;

int solve();

int main() {
  cin >> n;
  a.resize(n);
  for (auto &p : a) cin >> p;
  cout << solve() << endl;
  return 0;
}

int solve() {
  vector<int> v;
  queue<int> qu;
  sort(a.begin(), a.end());
  for (int i = 0; i < n; ++i) {
    while (qu.size() && qu.front() + 1 < a[i]) {
      v.push_back(qu.front());
      qu.pop();
    }
    if (v.size() && v.back() + 1 < a[i]) v.pop_back();
    qu.push(a[i]);
  }
  return v.size() + qu.size();
}